Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
With no annotations provided, the description carries the full burden of behavioral disclosure. It says 'List all runs' but does not mention pagination, return format, whether it includes archived runs, or any authentication requirements. For a listing tool, such omissions leave the agent uncertain about response size and handling.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.